a b s t r a c tThe onshore sector of the West Iberian Margin (WIM) was the locus of several cycles of magmatic activity during the Mesozoic, the most voluminous of which was of alkaline nature and occurred between 70 and 100 Ma. This cycle took place in a post-rift environment, during the 35 counter-clockwise rotation of Iberia and initiation of the alpine compression. It includes the subvolcanic complexes of Sintra, Sines, and Monchique, the volcanic complex of Lisbon and several other minor intrusions, covering an area of approximately 325 km 2 . Previous cycles were tholeiitic and transitional in nature, occuring around 200 Ma and 130-135 Ma, respectively. New LA-ICP-MS U-Pb, 40 Ar/ 39 Ar, K-Ar and Rb-Sr ages on several intrusions distributed along the onshore WIM are presented, which combined with previously published data allows us to constrain the duration of the Late Cretaceous alkaline cycle to circa 22 Ma (94-72 Ma) and define two pulses of magmatic activity. The first one (94-88 Ma) occurred during the opening of the Bay of Biscay and consequent rotation of Iberia and clusters above N38 20 0 . The second pulse (75-72 Ma) has a wider geographical distribution, from N37 to N39 . This final pulse occurred during the initial stages of the Alpine orogeny in Iberia that led to the formation of the Pyrenees and Betics and to tectonic inversion of the Mesozoic basins. Isotope and trace element geochemistry point to a sublithospheric source for the alkaline magmatism that clearly distinguishes it from the previous cycles which had an important lithospheric mantle component. Also, it allows the discrimination between the two different alkaline pulses in terms of trace element abundance and residual mantle minerology. It is speculated that these differences might be the result of distinct magma ascent rates due to either more or less favourable tectonic settings that avoided or allowed the interaction with metasomatized lithosphere and equilibration with K rich minerals like amphibole and/or phlogopite.

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The metasediment-hosted distal scheelite skarns from the Riba de Alva mine, Barca de Alva-Escalhão re gion, northeastern Portugal, consist of three main levels of strata-bound, boudin-shaped, 0.5-to 4-m-thick bod ies, having a total resource of 380,000 tons (t) with an average grade of 0.51 percent W03. The boudinage of the Cambrian metasedimentary rocks of the Siate Greywacke Complex occurred early during the Hercynian orogeny, prior to the Granitic Complex intrusion and the skarn-forming process. The Granitic Cornplex corre sponds to reduced, highly evolved, and metallogenically specialized S-type leucogranites, comparable to those commonly associated with Mo-poor W-F skarns.Four different skarn types were recognized: pyroxene skarn with Fe diopside ± anorthite; amphibole-epi dote skarns with actinolite + clinozoisite ± bytownite ± phlogopite; ore skarn with clinozoisite + scheelite + flu orite + calcite ± labradorite ± apatite ± Fe axinite ± armenite ± scapolite; and late-stage veins with quartz (or fluorite or calcite) ± clinozoisite ± andesine (or albite) ± adularia.Clinopyroxene ranges from Di80Hd29 to Di60Hd49. Amphibole compositions range from actinolite to Mg hornblende and are F rich (0.5-1.9 wt %). Clinozoisite, often zoned with Fe-poor cores, shows little composi tional variation in the skarn types, having a low pistacitic component (5-13% Ps). Plagioclase compositions grade from anorthite in pyroxene skarn through andesine and albite in late-stage veins. Phlogopite, as amphi bole, is F rich (2.45-4.70 wt %). Au extremely pure Mo-free scheelite, the only ore mineral present, is re stricted to the ore skarn type.The Riba de Alva skarns were formed, after intrusion of the Hercynian Granitic Complex, by selective infil trative metasomatic alteration of argillaceous dolomitic limestone. An early stage of prograde alteration led to the formation of the pyroxene skarn, through reaction with an Si-rich and Fe-bearing fluid. Scheelite mineral ization occurred during retrograde alteration, which was rnainly fracture controlled and is characterized by a pervasive infiltration metasomatism with minor diffusion in the skarn walls. This alteration started with hydra tion reactions to form amphibole-epidote skarns, probably under lower X~09 conditions. Ore skarn formation, with scheelite deposition, took place later during this retrograde stage, mainly along veins within the strata bound boudins, as the result of a decrease in temperature and/or significant changes in the activity of some fluid cornponents such as M/, F, Na, Mn, P, and B, and particularly an increase in aca. Monomineralic late-stage veins represent the waning stage of the skarn-forrning process.

Highly fractionated granites and related magmatic-hydrothermal ore-forming processes can be traced by elemental ratios such as Nb/Ta, K/Rb, Y/Ho, Sr/Eu, Eu/Eu*, Zr/Hf, and Rb/Sr. The lanthanide “tetrad effect” parameter (TE1,3) can also be a useful geochemical fingerprint of highly fractionated granites. This work assesses its application as an exploration vector for granite-related mineralization in the Central Iberian Zone by examining TE1,3 variations with different elemental ratios and with the concentrations of rare metals and fluxing elements (such as F, P, and B). The multi-elemental whole-rock characterization of the main Cambrian–Ordovician and Carboniferous–Permian granite plutons and late aplite–pegmatite dykes exposed across the Segura–Panasqueira Sn-W-Li belt show that the increase in TE1,3 values co-vary with magmatic differentiation and metal-enrichment, being the Carboniferous–Permian granite rocks the most differentiated, and metal specialized. The Argemela Li-Sn-bearing rare metal granite and the Segura Li-phosphate-bearing aplite–pegmatite dykes deviate from this geochemical trend, displaying TE1,3 < 1.1, but high P2O5 contents. The results suggest that mineralized rocks related to peraluminous-high-phosphorus Li-Sn granite systems are typified by TE1,3 < 1.1, whereas those associated with peraluminous-high-phosphorus Sn-W-Li (lepidolite) and peraluminous-low-phosphorus Sn-Ta-Nb granite systems display TE1,3 > 1.1, reaching values as high as 1.4 and 2.1, respectively.